The present disclosure generally relates to radio frequency (RF) detection and ranging and, more particularly, to miniaturization of handheld radar units to make them more practical for particular types of use.
Portable, handheld radars have been used for detection of hidden objects, e.g., objects such as weapons or people hidden behind a wall of a building. it may be desirable to be able to detect hidden objects in many situations, including for example, constitutionally supported government agency investigation of a premises containing buildings of unknown internal configuration, military intelligence scenarios, and fire and rescue situations. Ultra wideband (UWB) radar systems have shown a high degree of fitness for such types of use.
UWB impulse radar systems utilize pulse widths on the order of hundreds of picoseconds (trillionth of a second). Because such short pulses necessarily have very few cycles or even a single cycle of RF signal (such as a Gaussian monopulse), UWB radars may be considered to operate in the time domain as opposed to conventional frequency domain processing of received pulses. This time domain operation enables UWB radars to enjoy very fine range resolutions such as on the order of a fraction of a few feet or less. In addition, UWB radars have high power efficiency because of their low transmit duty cycle. Furthermore, UWB radars provide users with a very low probability of detection because their transmitted pulses occupy a relatively large bandwidth and thus have low power spectral density.
Some UWB impulse systems having a 5 GHz center frequency of the RF signal, even though being capable of handheld operation, have an antenna that may be larger and more bulky than desirable for effective use in some situations. Typical systems have focused on narrow band solutions (in contrast to ultra wideband) at higher frequencies. The same principle is applicable to UWB communication systems. As with radar systems, a virtual beam forming mechanism could be applied to omni-directional communication protocols and transform the communication system into a narrow beam width line of sight millimeter wave communication system. Again, the benefit of using virtual beam forming instead of actual physical beam forming would be the size of the antenna system and the fact that in lower RF frequencies where most of the omni-directional wireless systems are working—such as wireless USB or UWB wireless PAN (personal area networks) networks—actual beam forming is not practical or desirable. As can be inferred from the foregoing, there is a need to provide a handheld UWB radar unit using existing 5 GHz UWB radars and having a reduced antenna size not practical with a 5 GHz RF center frequency.